Fate of 212Pb Inhaled by Human Subjects

Abstract

Ten human subjects inhaled zlzPb carried on natural aerosols. Deposition in thc lung varied from 14 to 45% of the amount inhaled. Clearance from the lung to the systemic tissues occurred with an estimated half-time of 6.5 hr. The average 24-hr urinary excretion of $lzPb was 2.8 f 0.15% of the body contcnt. The total loss by fecal excretion adjusted to zero time averaged 3% body content. The lead absorbed from the lungs into the blood is in part fixed by the circulating red cells and in part distributed to other tissues. The red cell 21zPb burden grows to a steady state level which averages 50% of the total body burden. The results are interpreted to indicate that the clearance of radon daughters from the lung parenchyma by absorption into the blood has little dosimetric significance, whereas, in the case of thoron daughters, the average lung dose is reduced to less than half.

Oral succimer decreases the gastrointestinal absorption of lead in juvenile monkeys.

“…These latter results are consistent with studies in humans (33), monkeys (31), and rodents (34)(35)(36), and collectively demonstrate that endogenous fecal excretion is significant as a route of Pb elimination from the body. Effects of succimer on BPb level.…”

Risks to children from exposure to lead in air during remedial or removal activities at Superfund sites: A case study of the RSR lead smelter Superfund site†

“…The respiratory tract portion of the ICRP model is empirically based on experimental observations from inhalation studies conducted in adults, which revealed multicompartmental absorption kinetics for deposited lead (Hursh and Mercer, 1970;Hursh et al, 1969;Wells et al, 1975;Chamberlain et al, 1978;Morrow et al, 1980 ). In these studies, exposures were to particles having mass median aerodynamic diameters below 1 m and, therefore, deposition of the inhaled lead particles can be assumed to have been primarily in the bronchiolar and alveolar regions of the respiratory tract (James et al, 1994 ) where transport of deposited lead to the gastrointestinal tract is likely to have been only a minor component of particle clearance ( Hursh et al, 1969 ). The ICRP lead model includes four deposition compartments from which a total of 95% of deposited lead is absorbed with half -times ranging from 1 h to 2 days, and 5% is transferred to the stomach (Chamberlain et al, 1978 ).…”

Characterizing Golden Eagle Risk to Lead and Anticoagulant Rodenticide Exposure: A Review

“…The respiratory tract deposition and clearance from the respiratory tract have been measured in adult humans (Chamberlain et al 1978;Hursh and Mercer 1970;Hursh et al 1969;Wells et al 1975). In these studies, exposures were to lead-bearing particles having mass median aerodynamic diameters (MMAD) below 1 μm and, therefore, deposition of the inhaled lead particles can be assumed to have been primarily in the bronchiolar and alveolar regions of the respiratory tract (James et al 1994) where transport of deposited lead to the gastrointestinal tract is likely to have been only a minor component of particle clearance (Hursh et al 1969).…”

“…In these studies, exposures were to lead-bearing particles having mass median aerodynamic diameters (MMAD) below 1 μm and, therefore, deposition of the inhaled lead particles can be assumed to have been primarily in the bronchiolar and alveolar regions of the respiratory tract (James et al 1994) where transport of deposited lead to the gastrointestinal tract is likely to have been only a minor component of particle clearance (Hursh et al 1969). Approximately 25% of inhaled lead chloride or lead hydroxide (MMAD 0.26 and 0.24 μm, respectively) was deposited in the respiratory tract in adult subjects who inhaled an inorganic lead aerosol through a standard respiratory mouthpiece for 5 minutes .…”

“…Approximately 25% of inhaled lead chloride or lead hydroxide (MMAD 0.26 and 0.24 μm, respectively) was deposited in the respiratory tract in adult subjects who inhaled an inorganic lead aerosol through a standard respiratory mouthpiece for 5 minutes . Approximately 95% of deposited inorganic lead that is inhaled as submicron particles is absorbed (Hursh et al 1969;Wells et al 1975). Rates of clearance from the respiratory tract of inorganic lead inhaled as submicron particles of lead oxide, or lead nitrate, were described with half-times of 0.8 hours (22%), 2.5 hours (34%), 9 hours (33%), and 44 hours (12%) (Chamberlain et al 1978).…”